Robotic vehicle having tiltable propulsion units

ABSTRACT

An intervention vehicle of the type comprising propulsion units (4) that are tiltable by rotation about transverse carrying shafts (66), comprising advance and tilting driven shafts (8, 9) disposed coaxially inside each carrying shaft (66) and transmitting their motion via linear transmission elements (84, 90, 98) inside each propulsion unit for driving advance motion and tilting motion, and also constituting a speed reducer for the tilting motion. The invention is particularly applicable to the nuclear industry.

FIELD OF THE INVENTION

The present invention relates to a vehicle for interventions, inparticular in buildings.

It is particularly applicable in industrial installations where somekind of intervention is required and where it would be dangerous orimpossible for a human operator to go. The vehicle according to thepresent invention may then be provided with appropriate instruments suchas video cameras, measuring apparatuses, and tools, thereby constitutinga self-propelled robot.

The robot of the present invention may be particularly useful in anuclear power station or in a plant for reprocessing nuclear fuel,whenever it is necessary to undertake repairs or inspection operationsin zones that are subjected to high levels of ionizing radiation aftercertain operating incidents. However, such robots may also be useful inother industries, for example in the chemical industry if there is adanger of explosion, or for public safety operations or for surveillancepurposes, or robots used for service purposes, e.g., cleaningoperations, in agriculture or in military activities.

BACKGROUND OF THE INVENTION

An important quality for a vehicle of this nature is its ability to moveover rough ground, i.e., ground having obstacles to be overcome.Obstacles can arise in a wide variety of forms, for example a staircasedesigned for humans and which must be gone up or down, or a pipe thathas fallen on a floor. There are two main aspects to the safety of suchvehicles when they are overcoming such obstacles. One of them isstability, i.e., the ability of the vehicle to avoid toppling over underits own weight and the weight of its load. The other problem isadherence, and this applies to each of the vehicle propulsion units,i.e. the members of the vehicle that bear against the ground forsupporting the vehicle and for causing it to move or stand still.Adherence relates to the ability of these propulsion units to avoidslipping excessively on contact with the ground, even when the surfacestate of the ground is locally unfavorable.

Another important quality of such a vehicle is its size, in particularits transverse and longitudinal dimensions, which must be small enoughto enable the vehicle to travel along various passages or corridorsinside buildings that were designed for people only.

Another important quality is that the vehicle should be as light aspossible.

Various vehicles have been designed for overcoming obstacles safety. Afirst vehicle is disclosed in ACEC's EP 197 020 which describes aremotely controlled vehicle constituting a robot for performinginspections and interventions in hostile environments. The vehicle has adrive assembly, i.e., means for applying drive and braking, whichassembly is integrated in a main chassis of the vehicle. It alsopossesses means for transmitting the forward drive defined by said driveassembly to crawler tracks carried outside the chassis on propulsionunits themselves carried by the vehicle. The vehicle is fitted with twopropulsion units, one at the front and the other at the back, each ofthe propulsion units having two tracks mounted thereon, one on the leftand the other on the right. Each propulsion unit may be tilted relativeto the vehicle from the vehicle. Thus, if the robot encounters anobstacle head on, and the obstacle is of a moderate height that issubstantially constant in the transverse direction, then the vehicle canpass over the obstacle while maintaining the vehicle body in asubstantially horizontal position. However, if the vehicle encounters ahead-on obstacle that slopes steeply sideways, then it runs the risk oftoppling over sideways as it climbs over the obstacle.

A second known vehicle moves by means of legs in a "spider" typeconfiguration, thereby enabling it to overcome a very wide variety ofsmall obstacles. However, it moves very slowly because it is notpossible, in general, to move a plurality of the vehicle's legssimultaneously.

A third known vehicle has four crawler-track propulsion units eachcapable of being tilted relative to the body of the vehicle. The crawlertrack of each propulsion unit is guided over a certain number of guidemembers, in particular over two wheels, one of which is a drive wheelfor causing the crawler track to move forwards. These members arecarried by a housing which constitutes the structure of the propulsionunit and which is assembled to the body of the vehicle in such a manneras to enable the propulsion unit to be tilted about a transverse axis.The vehicle body carries drive assemblies including motors both fortilting and for forward motion, some of which assemblies drive the drivewheels via mechanical transmission systems and others of which drive thetilting movements of the propulsion units. These assemblies also includebrakes for controlling movement. The vehicle body also carrieselectrical power supply batteries and means for controlling the driveassemblies.

This third known vehicle is proposed by the Mitsubishi under the nameMRV (Multifunctional Robot Vehicle), and is described at pages 425 and426 in the proceedings of the "85 ICAR International Conference onAdvanced Robotics", Sept. 9-10, 1985, Tokyo, Japan, organized by theRobotics Society of Japan, The Society of Biomechanisms, and the JapanIndustrial Robot Association. It appears to be capable of overcomingobstacles of known shapes, and it seems to be capable of a forward speedconsiderably higher than that of the above-mentioned second knownvehicle. Nevertheless, it appears to present the above-mentionedimportant qualities to an insufficient extent only.

European patent application EP-A-0 206 930 describes a fourth knownvehicle comprising two pairs of propulsion units, one at the front andthe other at the back, these pairs of propulsion units being carried byfront and back portions of the vehicle body and each of them beingconstituted by two crawler track propulsion units, one on the right andthe other on the left. Each propulsion unit has two wheels, a frontwheel and a back wheel, a crawler track which is supported by and drivenby said wheels, and track support means between the two wheels.

This known vehicle is of variable configuration or geometry, in thesense that the front and back portions of the vehicle body are hingedrelative to each other about a middle transverse axis. This axiscoincides with the axis of the rear wheels in the front pair ofpropulsion units and with the axis of the front wheels in the back pairof propulsion units.

It is disclosed that obstacles can be overcome without compromising thestability of the vehicle by displacing its center of gravity and byaltering the realtive angular position of the two portions of thevehicle body.

Although this known vehicle does indeed appear to be capable ofovercoming obstacles without losing stability, this capability appearsto be somewhat limited.

SUMMARY OF THE INVENTION

A particular object of the present invention is to provide anintervention vehicle in a simple manner and suitable for overcoming avariety of obstacles safely, the vehicle being small in transverse size,thereby enabling it to follow passages designed for people. Theinvention also seeks to make it possible, by mounting tools on such avehicle, to provide a robot suitable for performing interventions invarious buildings, in particular after an accident has made the premisesinaccessible to a human operator.

More particularly, the invention seeks to enable such a vehicle toimpart tilting motion to its propulsion units when such motion isuseful, by using means that are lightweight and compact.

To this end, the present invention provides an intervention vehicle ofthe type comprising propulsion units that are tiltable by rotation abouttransverse carrying shafts, advance and tilting driven shafts beingdisposed coaxially inside each carrying shaft and transmitting theirmotion via linear transmission elements inside each propulsion unit fordriving advance motion and tilting motion, and also constituting aspeed-reduction means for the tilting motion.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention is described below with referenceto the accompanying diagrammatic figures, it being understood that theitems and dispositions described and shown are given purely by way ofexample. When an item appears in more than one of the figures, it isdesignated in all of them by the same reference numeral symbol.

FIG. 1 is a side view of a vehicle in accordance with the presentinvention.

FIG. 2 is a back view of the same vehicle.

FIG. 3 is a side view of a propulsion unit of the vehicle, with itsouter covers removed to show the transmission means inside thepropulsion unit.

FIG. 4 is a view of one of the sides of the bottom body of the vehiclewithout the propulsion unit, the drive means, or the control means.

FIG. 5 is a view showing a propulsion unit assembly plate constituting aportion of the side shown in FIG. 4.

FIG. 6 is a plan view of the propulsion unit shown in FIG. 3, with thecrawler track and the top guide components of the propulsion unit beingremoved.

FIG. 6A shows the central portion of FIG. 6 on a larger scale and insection on a horizontal plane.

DESCRIPTION OF PREFERRED EMBODIMENT

As shown in FIGS. 1 and 2, a robot vehicle of the present inventioncomprises a bottom body 1 and a top body 3 which together constitute avehicle body 2. The bottom body 1 is mounted on four crawler propulsionunits such as 4, 6, and 7 enabling the vehicle to move in a longitudinaldirection X. The bottom of the vehicle contains electrical power supplybatteries whose heavy weight and low position contribute to providingvehicle stability. As described below, motors are disposed above thebatteries and serve to drive the propulsion unit.

The top body 3 is wider than the bottom body in a transverse directionY. It contains components that are relatively light in weight, such asmeans 158 for forming support signals, means 160 for processinginformation, and communication means, together with electronic powercomponents, exteroceptive sensors and an inertia system (not shown). Avertical direction relative to the vehicle is represented by arrow Z.

The width of the top body is equal to the overall width of the bottombody when fitted with its propulsion units, thereby providing adequatevolume without increasing the overall width of the vehicle.

Some or all of the following advantageous dispositions are present inthe vehicle according to the present invention.

Propulsion unit connection means (described in greater detail below) arecarried by the vehicle body for carrying the propulsion units.

Each of the propulsion units such as 4 includes at least one transversedriven shaft 8 extending towards the vehicle body to receive mechanicaldrive from the body in the form of shaft rotation, thereby impartingforward motion to the propulsion unit for the purpose of propelling thevehicle.

The vehicle includes motors 10 and 12 carried by the vehicle body forproviding said mechanical drive to each of said propulsion units in theform of rotation applied to respective transverse drive shafts 14 and 16which rotate relative to said vehicle body.

Each driven shaft has external transmission means enabling each of saiddriven shafts to be driven by one of said drive shafts.

Advantageously, said external transmission means for causing one of saiddriven shafts 8, 9 to be driven by one of said drive shafts 14, 16 areessentially constituted by a scissor-like transmission comprising:

a transverse axis drive wheel 18, 20 mounted on said drive shaft;

a first linear transmission element 22, 24 extending from said drivewheel along a first branch of the compass-like transmissionsubstantially perpendicularly to the axis of said wheel, and driven bysaid wheel;

a transverse intermediate shaft 26, 28;

spacing-maintaining means 30 for maintaining a first distance betweensaid drive shafts 14, 16 and the corresponding intermediate shafts 26,28 and for maintaining a second distance between said intermediateshafts and the driven shafts 8, 9, while enabling the shafts 26, 28, 8,and 9 to move perpendicularly to their own axes;

an intermediate drive wheel 32, 34 driven by said first lineartransmission element and mounted on said intermediate shaft to drivesaid intermediate shaft;

an intermediate driven wheel 36, 38, mounted on said intermediate shaft;

a second linear transmission element 40, 42 extending from saidintermediate driven wheel along a second branch of the scissor-liketransmission substantially perpendicularly to the axis of said wheel anddriven by said wheel; and

a driven wheel 44, 46 driven by said second linear transmission elementand mounted on said driven shaft to drive said shaft.

In the vehicle described by way of example, the above-mentioned drivewheels and driven wheels, together with other wheels mentioned below,are sprocket wheels whose teeth engage links in chains which constitutesaid linear transmission elements. However, the linear transmissionelements could alternatively be constituted by belts, or by cog belts.

The external transmission means are thus made in a simple manner whichenables the propulsion units to be displaced through large amplitudesvertically and longitudinally. Simultaneously, the presence of suchtransmission means does not increase the width of the vehicle (orincreases it only a little), in particular when the vehicle has lateralpropulsion units disposed on either side of the vehicle body.

Another advantageous disposition is that said propulsion unit connectionmeans comprise, for each of said propulsion units 4:

a propulsion unit carrying structure 48 which is movable and guidedrelative to said vehicle body 2 to enable said structure to move intranslation in a direction perpendicular to said transverse direction Yover a range which is not less than an interval 60, said structurecarrying said propulsion unit; and

propulsion unit positioning means 50 for causing said propulsion unitcarrying structure to take up a controlled position within said range.

The displacement range may extend longitudinally only, vertically only,or in both directions, as described below.

Such a disposition makes it possible to stabilize the vehiclecontinuously as it moves over ground having varying slopes.

Another advantageous disposition is that said propulsion unit carryingstructure comprises:

a vertical guide structure (e.g., having rails 52) carrying saidpropulsion unit via a suspended bearing 49 and guided vertically toenable it to perform suspension displacement over one such displacementrange which is vertical; and

a longitudinal guide structure 54 carrying said vertical guide structurevia suspension means 56 to provide suspension for said vehicle, saidlongitudinal guide structure being guided longitudinally relative tosaid vehicle body 2 to enable it to take up any such controlled positionover a displacement range 60 which is longitudinal, thereby enabling thevehicle to be stabilized by displacing its center of gravitylongitudinally relative to said propulsion unit whenever said vehicle isgoing up or down a slope of the ground over which it is moving.

Another advantageous disposition is that said propulsion unit 4 standson the ground over a distance 58 which extends along said longitudinaldirection, with the propulsion unit being capable of bearing against theground to support said vehicle body anywhere between the two ends of thedistance 58;

said propulsion unit carrying structure 48 carrying said propulsion unitwhile enabling it to perform tilting movements 62 on command, whichmovements are constituted by rotation about a propulsion unit axis 64;

said vehicle comprising for each of said propulsion units 4:

a vehicle advance motor 10 and a tilting motor 12 provided respectivelywith an advance shaft 14 and a tilting shaft 16 constituting said driveshafts;

an advance driven shaft 8 and a tilting driven shaft 9 constituting saidtwo driven shafts and extending coaxially along said propulsion unitaxis 64; and

external advance 22, 40 and tilting 24, 42 transmission meansconstituted by said two scissor-like transmissions for driving saidadvance and tilting driven shafts from said advance and tilting driveshafts, respectively.

Said tilting motor constitutes a tilting actuator for the propulsionunit.

Tilting a propulsion unit may have the effect of displacing the meansupport point of the propulsion unit on the ground longitudinally and ofdisplacing the axis of the propulsion unit vertically relative to theground. Such tilting is intended to enable the vehicle to overcome anobstacle.

Another advantageous disposition is that said propulsion unit carryingstructure 48 includes a propulsion unit carrying shaft 66 extendingalong said propulsion unit axis 64 of said vehicle body 2 as far as saidpropulsion unit 4, the propulsion unit comprising:

a unit housing 68, 70 guided to rotate about said carrying shaft 66;

said advance and tilting driven shafts 8 and 9 guided to rotatecoaxially inside said carrying shaft;

a propulsion unit support assembly 72, 74, 76, and 80 for standing onthe ground over said ground support distance 58, said assembly includingat least one advance wheel 72 guided to rotate relative to saidpropulsion unit housing 68, 70 about a transverse axis;

internal advance transmission means 82, 84, 86 for driving at least saidadvance wheel from said advance driven shaft 8 in such a manner as toimpart said advance motion to said propulsion unit; and

internal tilting transmission means 88, 90, 92, 94, 96, 98, and 100carried by said propulsion unit housing, rotated by said tilting drivenshaft and applying rotary reaction against said propulsion unit carryingshaft in order to impart said tilting motion to said propulsion unit.

Another advantageous disposition is that said separation maintainingmeans for maintaining a distance between two shafts comprise:

a rod 30 bearing against both shafts 28 and 9 while allowing each ofthem to rotate; and

separation adjustment means for giving said rod either a working lengthfor tensioning a flexible linear transmission element such as the driveor driven chain 42 or such as a transmission belt performing the samefunction, or else an assembly length which is shorter than said workinglength in order to enable said connection element to be assembled ordisassembled. These means are symbolized by a screw 31 and a nut 31A.Other rods performing similar functions are referenced 30A, 30B, and30C. Analogous length adjusting means are associated with these otherrods.

Another advantageous disposition is that for each of said lateralpropulsion units 4, an assembly plate 102 of the propulsion unit isremovably fixed to said vehicle body 2, the plate extending in saidlongitudinal and vertical directions X and Z and carrying said advanceand tilting motors and drive shafts 10, 12 and 14, 16 together with saidexternal advance and tilting transmission means 22, 40 and 24, 42.

This assembly plate carries the longitudinal guide structure such as 54which carries an intermediate portion 48A of the carrying structure 48which itself carries the vertical guide structure having the rails 52.This structure carries a rectangular suspended bearing 49 which isrotatably mounted on the carrying shaft 66.

The vehicle has four of said lateral propulsion units, namely a frontright unit 4, a front left unit, a back right unit 6, and a back leftunit 7, and four of said longitudinal guide structures, namely a frontright structure 54, a front left structure, a back right structure 55,and a back left structure corresponding to respective ones of the fourpropulsion units. In this case, another advantageous disposition is thatthe said positioning means of a propulsion unit include positioncoordination means 50, 104 for coordinating the positions that two ofsaid propulsion units are instructed to take up by means of the two saidcorresponding horizontal guide structures 54 and 55.

Another advantageous disposition is that for each of the two pairs ofpropulsion units on one side or the other of the vehicle, i.e. for thefront right and back right propulsion units 4 and 6 or for the frontleft and back left propulsion units, said propulsion unit positioningmeans comprise:

a longitudinal linking spacer 108 interconnecting the two horizontalguide structures 54 and 55 corresponding to the two propulsion units ofthe pair;

a longitudinal positioning screw 104 also interconnecting the two guidestructures;

a rotary drive nut 106 co-operating with said screw and fixed inlongitudinal position relative to said vehicle body 2; and

a motor 50 for rotating said drive nut.

This motor constitutes a propulsion unit positioning actuator common tosaid two pairs. By means of a chain 110 it drives a transverse shaft 112which drives one of said two drive nuts such as 106 at each of its twoends, said nuts being driven via respective angle gear drive devicessuch as 114.

Another advantageous disposition is that said internal tiltingtransmission means comprise at least:

a first drive wheel 88 mounted on said tilting driven shaft beyond saidcarrying shaft 66;

a first linear transmission element 90 driven by said first wheel;

an intermediate internal tilting transmission shaft 92 extendingtransversely and guided to rotate relative to said propulsion unithousing; a first driven wheel 94 mounted on said intermediate shaft anddriven by said first liner transmission element to rotate said shaft;

a second drive wheel 96 mounted on said intermediate shaft;

a second linear transmission element 98 driven by said second drivewheel; and

a tilting support driven wheel 100 co-operating with said secondtransmission element and fixed, at least angularly, on said carryingshaft to cause said intermediate shaft and said propulsion unit housingto rotate about said carrying shaft, thereby driving said tiltingmotion.

Another disadvantageous disposition is that said drive wheels 88 and 96of the internal tilting transmission means have smaller diameters thansaid driven wheels 94 and 100 so that said transmission means alsoconstitute speed-reducing means so that the speed of rotation of saidtilting motion is less than that of said tilting driven shaft, therebylimiting the forces that need to be applied by said tilting motor 12 tosaid external transmission means when driving said tilting motion.

In said internal transmission means, as in said external transmissionmeans, the drive wheels and the driven wheels are constituted bysprocket wheels and said linear transmission elements are constituted bychains.

Another disposition is that said ground support assembly in each of saidlateral propulsion units comprises:

a crawler track 80 bearing against the ground;

means 72, 74, 76, and 78 for guiding the crawler track; and

an advance wheel 72 rotating about a transverse axis for driving saidtrack.

More precisely, this assembly comprises the advance wheel 72 and a guidewheel 74 at opposite ends of said support distance, intermediate supportwheels such as 76, and deflection wheels such as 78 for guiding thetrack 80, with ground contact being made solely by the track 80. Thetrack has inside teeth and the wheels 72 and 74 are sprocket wheelswhose teeth engage in the teeth of the track.

Another advantageous disposition is that said internal advancetransmission means comprise:

a drive wheel such as a first sprocket wheel 82 carried by said advancedriven shaft 8 beyond said carrying shaft 66;

a linear transmission element such as a chain 84 driven by said firstsprocket wheel; and

a driven wheel such as a second sprocket wheel 86 fixed to said advancewheel 72 and driven by said chain to drive advance motion of thepropulsion unit 4.

These two wheels are shown as having the same diameter, but theirdiameters could be different, e.g. to constitute a speed reduction gear.

Other advantageous dispositions adopted in the same vehicle relate tothe signal processing and measurement means with which the vehicle isequipped. In this context, it is recalled that each propulsion unit issupported by the ground by means of a set of forces which may usefullybe represented, at least in part, by a certain number of parameters.These parameters are referred to below as "support parameters".

One of these advantageous dispositions is that, in order to determine acertain number of ground support parameters of one of said propulsionunits 4, force signals are formed representative of the forces appliedto said propulsion unit from the body of the vehicle 2, and these forcesignals are processed in order to form support signals representative ofthe support parameters to be determined.

More particularly, at least three of said force signals are formedrepresentative of the forces applied to any one of said propulsion units4 by said vehicle body 2, and these force signals are processed to formthree of said support signals representing three of said supportparameters which themselves represent the component of said supportforce of said propulsion unit in a longitudinal vertical plane.

To this end, the vehicle includes force sensors 150, 152, and 154 forforming said force signals; and

support signal forming means 158 receiving and processing the forcesignals to form said support signals. Said support signals represent,for example, said component of said support force in terms of its angle,the longitudinal position of its point of application on the ground, andits magnitude.

Another advantageous disposition is that said carrying shaft 66 ismounted in the suspended bearing 49 which constitutes a portion of thecarrying structure 48 in such a manner as to be guided in rotation aboutsaid propulsion unit axis 64. More particularly, the carrying shaft 66is mounted to rock in the suspended bearing 49 which is guidedvertically relative to the carrying structure 48 by means of thevertical guide structure 52. The vehicle then includes a tilting forcesensor 152 which constitutes one of said force sensors and which ismounted between said carrying shaft and a non-rotating portion of thecarrying structure so as to prevent said shaft from rotating, therebyproviding a tilting force signal representative of a tilting momentapplied to said propulsion unit 4 by said vehicle body 2.

Another advantageous disposition is that an advance force sensor 154 isassociated with said advance motor 10 or with said external advancetransmission means 22, 40 to provide an advance force signalrepresentative of an advance torque applied by said external advancetransmission means to said advance driven shaft 8, such that said forcesignal is suitable for use in determining the component of said supportforce which is tangential to the propulsion unit in a longitudinalvertical plane.

Another advantageous disposition is that a vertical force sensor 150 isassociated with said vertical guide structure to provide a verticalforce signal representative of a relative vertical force applied to saidpropulsion unit 4 by said vehicle body 2 in a relative verticaldirection related to said vehicle body, such that said vertical forcesignal is suitable for use in determining the force of said supportforce which is normal to the support surface of the propulsion unit.

Another advantageous disposition is that said vehicle further includesconfiguration sensors 156 for providing configuration signalsrepresentative of configuration parameters such as the position and/orthe angle of each of said propulsion units relative to said vehicle body2 and/or the orientation of the vehicle body relative to the vertical,said support signal forming means 148 also receiving and processing saidconfiguration signals in order to form said support signals.

One of said configuration sensors is an angle sensor 156 carried by thevehicle body 2. It measures the angle of rotation of the housing 70 ofthe propulsion unit 4 about the propulsion unit axis 64 by means of agear wheel 155 which is coaxial with the sensor 156 and whichco-operates with a gear wheel 157 fixed to the housing 70. This sensorprovides a propulsion unit angle signal representative of the angle ofthe propulsion unit relative to the vehicle body.

Another of said configuration sensors is a longitudinal position sensor51 (see FIG. 4) which measures the longitudinal position of said set ofpropulsion units relative to the vehicle body 2 and which provides alongitudinal position signal.

It is apparent from the above description that the vehicle includespropulsion unit displacement actuators 12 and 50 for displaceing saidpropulsion units relative to said vehicle body, and means for formingsupport signals representative of said support parameters.

Another advantageous disposition is that it further includes safetycontrol means constituting a portion of the information processing means160 and making use of said support signals for controlling saiddisplacement actuators so as to improve vehicle safety.

These displacement actuators comprise said positioning actuatorconstituted by the motor 50 and the four tilting actuators constitutedby the four tilting motors such as 12.

Another advantageous disposition is that said safety control means 160make use not only of said support signals but also of speed signalsrepresentative of the speeds of said propulsion units 4, said vehicleincluding speed sensors for providing said signals.

Another advantageous disposition is that said safety control means 160control not only said displacement actuators 12, 50, but also saidadvance motors 10. More precisely, said control means evaluate at eachinstant firstly a current degree of safety, i.e., they determine in realtime values for safety parameters representative, in particular, ofvehicle stability and adherence. This is determined, in particular, as aresult of some of said support parameters. For example, stabilitydepends on the position of the vertical projection of the center ofgravity onto the support polygon defined by the support points of thepropulsion units. For each of the propulsion units, adherence depends onthe angle made by the support force passing through said propulsion uniton the ground and relative to a support surface. Secondly, the controlmeans 160 evaluate the influence that displacement of the propulsionunits or changes in the advance torques will have on the safetyparameters. Finally, the control means issue commands for optimizing thesafety parameters.

We claim:
 1. An intervention vehicle comprising:(a) a vehicle body (2)having a length and a width extending respectively along a longitudinaldirection (X) and a transverse direction (Y); (b) propulsion units (4,6) resting on the ground in operation to suport said vehicle body and tohave an advance motion along said longitudinal direction; (c) saidvehicle comprising for each of said propulsion units (4):(i) apropulsion unit carrying shaft (66) carried by said vehicle body (2) andcarrying a propulsion unit housing (68, 70) while enabling it to performa tilting motion (62) on command about a transverse tilting axis (64) ofsaid propulsion unit; (ii) an advance motor (10) and a tilting motor(12) carried by said vehicle body (2); and (iii) an advance driven shaft(8) and a tilting driven shaft (9) driven by said advance motor and bysaid tilting motor, respectively, and extending coaxially into saidpropulsion unit along said tilting axis inside said propulsion unitcarrying shaft; (d) each said propulsion unit further comprising:(i) anadvance wheel (72) guided to rotate relative to said propulsion unithousing (68, 70) about a transverse axis at a distance from said tiltingaxis in such a manner as to impart said advance motion to saidpropulsion unit; (ii) internal advance transmission means (82, 84, 86)for driving said advance wheel from said advance driven shaft (8); and(iii) internal tilting transmission means; (e) said internal tiltingtransmission means comprising(i) a first drive wheel (88) mounted onsaid tilting driven shaft beyond said carrying shaft (66) for rotatingat a first tilting transmission angular speed; (ii) a first lineartransmission element (90) driven by said first wheel; (iii) anintermediate shaft (92) extending transversely and guided to rotaterelative to said propulsion unit housing; (iv) a first driven wheel (94)mounted on said intermediate shaft and driven by said first lineartransmission element to rotate said shaft; (v) a second drive wheel (96)mounted on said intermediate shaft; (vi) a second linear transmissionelement (98) driven by said second drive wheel; and (viii) a tiltingsupport driven wheel (100) cooperating with said second transmissionelement and fixed, at least angularly, on said carrying shaft to causesaid intermediate shaft and said propulsion unit housing to rotate aboutsaid carrying shaft in such a manner as to drive said tilting motion ata tilting angular speed which is less than said first tiltingtransmission angular speed.
 2. A vehicle according to claim 1, whereineach of said propulsion units (4) stands on the ground over a groundsupport distance (58) which extends along said longitudinal direction,with the propulsion unit being capable of bearing against the ground tosupport said vehicle body at any point of said ground support distance(58).
 3. A vehicle according to claim 1, wherein said first and seconddrive wheels (88, 96) of the internal tilting transmission means havesmaller diameters than said first and second driven wheels (94, 100),respectively.
 4. A vehicle according to claim 1, wherein said groundsupport assembly in each of said lateral propulsion units comprises:(a)a crawler track (80) bearing against the ground; (b) means (72, 74, 76,78) for guiding said crawler track; and (c) an advance wheel (72)rotating about a transverse axis for driving said track.
 5. A vehicleaccording to claim 4, wherein said internal advance transmission meanscomprise:(a) a drive wheel (82) carried by said advance driven shaft (8)beyond said carrying shaft (66); (b) a linear transmission element (84)driven by said drive wheel; and (c) a driven wheel (86) fixed to saidadvance wheel (72) and driven by said transmission element to driveadvance motion of said propulsion unit (4).